Ridge vent is a simple addition that can increase air flow within your garage. It can easily be installed on an existing roof or put in place at the time of construction. When properly installed, a ridge cap sets up a nice flow of air out of the building, which will keep the enitre building well ventilated.
Most on summer months leave the garage door open, because it gets to hot. This invites critters and other crawling creatures to come in.
Like was mentioned in other post above, if they decide to finish the garage and heat it, ventilation requirement has been incorporated already, so there is the savings. Plan for the future. :)